1. Field of the Invention
The present application relates generally to oil field devices and, more particularly, to a plunger assembly with an expandable seal.
2. Description of Related Art
The oil and gas industry has been drilling holes and removing natural crude oil for decades. Wells contain any number of contaminants, particulates, and water along with the gas/oil being sought. If water is not removed, pressure of the hydrostatic head of water in the surface tubing will become greater than that of the bottom hole pressure, thereby essentially sealing the formation and shutting in the well. Gas cannot on its own pressure typically flow to the surface.
Plungers are downhole tools used by operators to remove contaminants and water from productive natural gas wells. A plunger acts as an artificial lift. In operation the plunger passes down through the well until it reaches a contact point, at which point, potential energy of the plunger falling in the well acts to partially restrict the flow of working fluid through the plunger. Pressure beneath the plunger builds and raises the plunger in the well, thereby pushing out the liquids and contaminants above the plunger.
Typical plunger lift systems are inefficient partly due to the design constraints placed upon tool designers. A major limitation placed upon tool designers are the design constraints related to tubing tolerances within the well bore itself. Tubes come in different diameters (tolerance variation) and in set lengths (i.e. 30-34 feet). Tubing tends to not be perfectly straight, round, or have the exact same internal diameter. Variations in tubing internal diameters and at junction points between tubes result in a term called “drift diameter”. The drift diameter is the minimum inside diameter of the tube in order to pass a ridged tool of some set length through it. Tools are designed to have a maximum diameter no greater than the drift diameter of the tubing. This results in the tools having a gap between them and the ID of the tubing. The large annulus or gap between the tool and the tubing that the tools passes through are why tools tend to be inefficient because plunger lift tools work on a pressure gradient between fluid beneath the tool and fluid above the tool. Leaks between the tool and tubing impact the pressure gradient.
Another disadvantage of conventional plunger lift systems are the particulates (i.e. sand) in the working fluid. The working fluid passes within the gap between the plunger lift system and the casing at increased speeds resulting in tools abrading quickly. Additionally, the leak leads to turbulence created around the down hole edge of the tool when it expands after passing through the leak. A new plunger lift assembly tool is required to minimize abrading and that corrects for the constraints associated with the drift diameter.
Although great strides have been made, considerable shortcomings remain.
While the assembly and method of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the application to the particular embodiment disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the process of the present application as defined by the appended claims.